The basic entrained flow process is described in my U.S. Pat. No. 4,343,775 of Aug. 10, 1982. Therein certain powdered anthracite-derived reductant is used in a downflow chlorination zone with such vaporous chorinating agent and titaniferous powder at elevated temperature. The fundamental stoichiometry of that chlorinating operation can be exemplified fairly fundamentally by the following equations I and II wherein chlorine gas reacts with titanium dioxide and solid carbon: EQU TiO.sub.2 (s)+2Cl.sub.2 (g)+C(s).fwdarw.TiCl.sub.4 (g)+CO.sub.2 (g) I. EQU TiO.sub.2 (s)+2Cl.sub.2 (g)+2C(s).fwdarw.TiCl.sub.4 (g)+2CO(g) II.
Iron is a common impurity in many titaniferous feeds for the present operation. An entrained flow process can chlorinate titanium and iron values simultaneously according to the stoichiometry exemplified and generalized by the following enumerated equations wherein the titaniferous feed is FeTiO.sub.3 particles: EQU 2FeTiO.sub.3 (s)+6Cl.sub.2 (g)+3C(s).fwdarw.2TiCl.sub.4 (g)+3CO.sub.2 (g)+2FeCl.sub.2 (g) III. EQU FeTiO.sub.3 (s)+3Cl.sub.2 (g)+3C(s).fwdarw.TiCl.sub.4 (g)+3CO(g)+FeCl.sub.2 (g) IV. EQU 2FeTiO.sub.3 (s)+7Cl.sub.2 (g)+3C(s).fwdarw.2TiCl.sub.4 (g)+3CO.sub.2 (g)+2FeCl.sub.3 (g) V. EQU 2FeTiO.sub.3 (s)+7Cl.sub.2 (g)+6C(s).fwdarw.2TiCl.sub.4 (g)+6CO(g)+2FeCl.sub.3 (g) VI.
As would be evident to one skilled in this art, some vaporous organochloride present, such as carbon tetrachloride, would be expected to supply some carbon and chlorine for the reaction, and a titaniferous feed of other specific composition also would call for adjustment in reactant feeds.
U.S. Pat. No. 4,343,775 points out that the entrained downflow reaction proceeds apace with fresh, finely-divided anthracite-derived reductant having micropores (i.e., pores having effective diameter of 20 .ANG. or less in size) that provide a substantial proportion of the carbon surface area of such fresh feed. Furthermore, in my copending U.S. patent application entitled "Chlorination of Titanium Ores Using Lignitic Reactive Carbons", Ser. No. 442,284, of even date herewith, it is pointed out that porous lignitic-derived carbon (such as char from brown coal or lignite) has an unexpected advantage relative to anthracite-derived reductant, namely that of substantially maintaining its useful surface area when it is employed to chlorinate titaniferous materials such as ore in a conventional fluidized bed operation. Thus, as such lignitic char-employing fluidized bed operation continues, the activity of such reductant resists deterioration rather than tending to deteriorate as could occur when anthracite-derived reductant is employed in such bed.
Other of my U.S. patents relevant to chlorination of titaniferous materials include: U.S. Pat. Nos. 4,183,899; 4,279,871; 4,310,495; and 4,329,322. The teachings of all the patents cited above are expressely incorporated by reference into this application.
Advantages of the instant improvement include not only those obtainable from an entrained downflow chlorination of titaniferous material like that of U.S. Pat. No. 4,343,775, but also a more rapid reaction than that of such patent with attendant economies, such as to apparatus and/or throughput. Also, in one aspect, namely that of using carbonaceous reductant derived from low-rank coal such as lignite like the porous reductant of Ser. No. 442,284, substantial adverse change in the surface area of the carbon can be averted. In fairness, though, it must be pointed out that such benefit in connection with the instant improvement would not be expected to be of the same large magnitude that can occur in connection with the fluid bed process of said companion application.